Parker was shot and killed by Antonio Milow, an off-duty Denver Police officer. Milow is a member of the church and is the pastor's cousin and Echols' nephew.

The Arapahoe County Coroner's office says Parker and Echols both died from multiple gunshot wounds.

9NEWS has learned Parker has an extensive criminal history that includes several felony charges for buying and possession of drugs including cocaine. He had been arrested in several jurisdictions, including Denver, Aurora, Arapahoe and Adams counties. He had been to jail several times.

Parker was last released from jail in October 2011 in Oklahoma after he served time for charges of assault and battery of a police officer and several counts of burglary.

Parker would have been locked up until 2021 in Oklahoma, but his sentence was suspended after a judicial review.

"It started somewhere on Dartmouth and [when Parker] became upset. We actually don't know why he became upset or where exactly this all started, but he became upset and took in his car at a high rate of speed. At that time he was he was with his friend who was he was concerned of his welfare and his actions and wanted to follow him to make sure he was alright," Officer Frank Fania with the Aurora Police Department said.

Officers say Parker went down an alley way and ended up in the church's parking lot.

Police say there is no connection between Parker and the church.

They say a friend was following Parker in another vehicle, but he lost track of him. The friend told police he didn't find Parker again until after the shooting.

Parker's car had hit another car in the parking lot. Pastor De Lono Straham told 9NEWS on Monday church members heard the noise of a car crashing outside. Someone asked his mom, who was a nurse, to go and help.

Echols, Straham's mother, was shot by Parker in the parking lot when she went outside.

"We don't know why the gunman did this. All the witnesses we've talked to said the gunman made no comments whatsoever," Fania said.

Straham says Parker made it as far as the foyer of the church after shooting Echols. That is when Parker was shot by Milow.

Both Echols and Parker were taken to local hospitals, where they were pronounced dead.

Tarell Martin, a musician with the Destiny Christian Center, told 9NEWS on Monday he was the first one out of the church, before Echols. He says Parker started to chase after him in the parking lot while pulling the trigger.

"When I fell on the ground, I tried to get up real quick, but he was already on top of me with a gun to my head, and he started shooting again, but no bullets came out," Martin said.

While Parker fiddled with the gun, Martin says he was able to get away. Then, the gun started working.

"He just started shooting at me as I was running towards the church," Martin said.

Martin escaped with a bruised arm from his encounter with the suspect.

Denver Police say Milow will be on paid administrative leave, which is standard procedure when officers are involved in shootings.

In 2010, Milow was part of a lawsuit against the city after a man said he was punched and kicked outside of a nightclub by Denver Police officers in 2007.

Eric Winfield of Denver says he was walking through a crowd outside a club on Oct. 27, 2007, when a bouncer mistakenly pointed him out as someone who had caused a disturbance there. Winfield said officers attacked him, leaving him with injuries including a broken nose, chipped teeth, two black eyes, and bruised ribs.

Milow said in a deposition that he acted after Winfield took a swing at him and kneed him in the groin.

Winfield initially was arrested on suspicion of resisting arrest and assaulting an officer, but charges were dismissed.